Emotiva BasX A-100 Stereo Flex Amplifier Review

This is a review of the headphone output of the Emotiva BasX A-100 Stereo Flex Amplifier. If you’re not familiar, Emotiva makes some great audio products at incredibly attractive price-points. They offer a host of speakers, headphones, amplifiers, processors, and other gear. I have owned their portable DACs which are a tremendous value; I ended up parting ways for lack of need. They were quite good sounding though and offered a robust build quality. I currently have some of their power equipment which is also well built. If I were a home theater afficionado, I’d likely have even more of their gear.

Emotiva has a value-oriented 2 channel amp called the BasX A-100. Normally it is a speaker amp providing 50 watts per channel into 8 Ohms and 80 Watts per channel into 4 Ohms, which is plenty for most setups. What is also pleasing for those with limited in-house real-estate is that the unit is half width, so 8-1/2” wide x 3.125” high x 15” deep. That saves half of your shelf for another piece of equipment/some headphones or something else.

Perhaps what is most interesting about the A-100 is that it can be used as a high-powered headphone amp. Granted, very few people would need this capability, but it is there. The unit does need to be internally jumpered for this operation as it is unsafe for standard headphones. The output is:

8 Ohms:  50 watts / channel
33 Ohms:  12 watts / channel
47 Ohms:  8.5 watts / channel
150 Ohms:  2.6 watts / channel
300 Ohms:  1.3 watts / channel
600 Ohms:  0.6 watts / channel

So, what headphone owners would be interested in this feature? Owners of low-sensitivity headphones like the HiFiMan Susvara, HiFiMan HE-6 or HE-6se, the HEDDPhones, the Abyss AB-1266, and others.

Normally I use an external box with some high quality resistors to convert a speaker amp’s output for headphones (it has some protections built in for amps with output transformers) but given the low cost of the A-100, it was a no-brainer to at least try it out.

Starting with the good news, the A-100 produced plenty of usable volume with the HE-6se and drove them with spades. There are some caveats though. The first, I noticed the amp takes a bit of time to warm up. When listening immediately, the midrange wasn’t well defined. After 10-15 minutes this seems to go away. Second, I found the sound to be fairly cool/bright and slightly lacking on the low end. This isn’t a big deal if you don’t mind EQing. I found reducing the upper midrange and increasing the low range to help make the sound more agreeable for my personal preferences. If you are listening from a computer, you can use the free program PEACE to make adjustments, if not, you can pick up something like the JDS Labs Subjective3 or the Schiit Loki. Neither of these offer an ideal level of control to get the A-100 exactly right (for me), but they are well made and get the job done affordably.

Running the HifiMan HE-6se with the Emotiva A-100

It seems that perhaps the weakest link of the A-100 is its potentiometer (volume control). Early into turning it, there was very noticeable channel imbalance. This seemed to subside quickly as the volume rose; however, it is important to note. A good potentiometer can be costly, so this was likely a price point issue. Given an Alps Blue Velvet (RK27), a frequently used entry-level potentiometer for audio, is around $12 per piece in bulk, it would be very hard to implement at this price level.

You get a lot for your money in terms of parts and build

Overall, the Emotiva BasX A-100 Stereo Flex Amplifier is impressive at its price point given the heft, solid and attractive build, and ability to send 50 WPC to a pair of headphones. Also the internal rectified power supply (no wall wart) is typically reserved for more expensive gear. If you were in the position to have purchased some HiFiMan HE-6 or HE-6se and had very little left over for a suitable amp, this is probably the only game in town, aside from potentially the balanced output of the Schiit Magnius which I haven’t yet tested.

If you were only interested in powering speakers and don’t mind purchasing used gear, you might want to cross-shop an older receiver from a reputable brand like Yamaha, Onkyo, Outlaw, or Denon. If you are DIY-minded, a chip amp like Akitika is a good route to investigate for speakers.   

If you are trying to power low-sensitivity headphones via a speaker amplifier, please check out the CBOX at Zynsonix.com. It provides a safe consistent load for your amplifier while delivering the juice your headphones need. 

Speaker Amp to Headphone Cable

I'll be showing off a rather unique audio cable today: a cable that connects the outputs from a speaker amplifier to a pair of headphones. You may be wondering why someone would be using a speaker amp for a pair of headphones. A typical headphone amplifier will output relatively a small amount of power compared to the speaker amplifiers (in small fractions of a watt measured in milliwatts). The Audeze, as well as certain other planar magnetic headphones like the HiFiMan, really benefit from some added wattage to sound their best as they aren't the most sensitive drivers. Hense, in some cases using speaker amplifier can be worthwhile.

Obviously speaker amps were made with speakers in mind, so there will be compromises involved. First and foremost, one can blow out or damage sensitive headphone drivers if turning up the amplifier volume too high. There are also some impedance differences, typically a speaker amplifier outputs at 8 ohms (and in some cases 4 or 16) while headphones will typically range from 35 to 600 ohms. Another factor to consider is that speaker amplifiers may not have a quiet black "background" when used with headphones due to noise, magnetic flux from the transformers or other reasons. Even still, with all of these factors, many audio enthusiasts still prefer listening through their speaker amp.

I'm starting out with some thicker-than-typical wire to braid. Using thicker wire not only assists in delivering a little more juice to the headphones but makes the soldered (or screwed in some cases) connection to the spades or bananas at the speaker amp end of the cable stronger. With a thin 24 gauge wire that would typically be used as a headphone cable, the joint would not be able to take as much abuse as a thicker, heavier wire. 

Silver plated copper with a thick dielectric

This wire is braided and an unbalanced Neutrik locking female is soldered in place. Note that an unbalanced connector is okay for use as the speaker amp has shared grounds (the left and right ground are connected with no resistance), otherwise this would not be acceptable and a balanced connector would be required. Note below that the two ground connectors are soldered together to the ground pin.

Braided silver plated copper in PTFE wire

The cable is now sleeved with the typical Techflex brand Nylon Multifilament in the 1/4" size and heatshrink is applied at both ends. I think it's visually appearing how the cable geometry is fully visible thanks to the tightness of the sleeving. The four lengths of wire are left unbraided at the end for the amp-side connections (sometimes the binding posts can be spaced relatively far apart). 

Sleeved with black nylon multifilament

The white wire was then covered with thin black heatshrink to match the color of the rest of the cable. Note that the heatshrink, just like Teflon tubing, can be resistant over long distances and can require a bit of patience. Once in place, a heat gun is used to shrink it down by starting at one end and moving to the other to avoid air bubbles getting trapped in the middle. 

Speaker ends being prepared

Now the spades could be soldered on. These particular spades are made by LOK and available at Homegrown Audio. They're gold plated and feature a high copper content (over 68%) and fit a 1/4" or 3/8" binding post. Each connector is labelled "L" for left, "R" for right and "G" for ground.

Below are photos of the final cable

Completed cable

And here is an example of the same type of cable for balanced operation. this particular cable uses a Neutrik locking female and rhodium plated spades.

Balanced 4 pin cable to rhodium spades

Need one and don't want to mess with a soldering iron? Zynsonix offers custom-made speaker amp to headphone cables (and many others), please contact them for a quote.


The Fine Print:
The above steps detailing the building of a cable are for entertainment purposes only, and not to be performed under any circumstances. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. Please keep this in mind.